<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <script>
      function A() {
        console.log(1);
      }

      function fn() {
        A = function () {
          console.log(2);
        };
        return this;
      }
      fn.A = A;
      fn.prototype = {
        A: () => {
          console.log(3);
        },
      };

    
      A();//1
      fn.A();//1
      fn().A();//2
      new fn.A();//1
      new fn().A();//3
      new new fn().A(); //报错
    </script>
  </body>
</html>
